The usual treatment of passwords and similar secrets on the GUI screen is that
the actual secret is not displayed, so a passer-by can't learn it.
Often we have talked about the idea that this non-echo should be relaxed
when the display is only by private (earphone) audio.
What I don't know is whether there is any actual practice making this
exception.
One place it could show up is in talking ATMs.
When there is an earphone plugged into a talking ATM, does the screen go blank?
Does the PIN echo in the earphone as you enter it?
[experience with a live ATM is most sought]
Al